Technical Abstract:
The oxidative and thermal behavior of veg. and mineral oils differs mainly due to their organic origin and hydrocarbon composition. The triglyceride structure associated with most veg. oils has poor oxidative stability with a completely different mechanism and texture of insoluble deposit formation as compared to mineral oils, which are primarily hydrocarbons of different shapes and sizes. Since oxidation and deposit forming behavior for any base oils, irrespective of their origin, is crucial for their being considered for lubricant application, a clear understanding is required of the molecular composition of such oils and their plausible behavior under high thermal environment. The high temp. thermal and oxidative degradation pathway have been mapped for a series of veg. and mineral oil basestocks, for their use as lubricant base oils. The current study was conducted under thin film condition in a micro reactor (25 microliter, 175, 200C, 1 hr and high carbon steel catalyst), and the thermal behavior of oils were determined on the basis of their structural diversity. Significant variation in the evaporation rate (using micro reactor) and nature of insoluble deposit was observed through Scanning Electron Microscope. Gel Permeation chromatography with an IR and UV detector was used to obtain the molecular weight distribution of the tetrahydrofuran soluble oxy compounds generated during oxidation. The structural parameters obtained using quantitative 1H and 13C NMR spectroscopy on the oxidized and unoxidized oils gave valuable information on the molecular composition and reaction pathway of the oils in terms of average structural parameters.